D6AC AlloySpecialty Alloys - High-Strength Alloy SteelsNominal Analysis0.46 C, 0.25 Si, 0.75 Mn, 1.10 Cr, 0.60 Ni, 1.00 Mo, 0.10 V, Bal. FeA medium carbon, low alloy, ultra high-strength steel primarily used for high strength structural applications requiring strength levels up to 280,000 psi. This alloy provides a high yield strength to tensile strength ratio, combined with good ductility. A tough and fibrous fracture is exhibited to as low as -210F (-134°C) in impact testing; also the notch toughness is excellent. It has been selected for fracture toughness critical applications at a variety of strength levels. The deep hardening characteristics has enabled the production of relatively large sections.D6AC Vac-Arc steel is produced by consumable electrode vacuum arc remelting process to impart cleanliness and preferred ingot structure, which in turn improves transverse mechanical properties.
美國于60 年代初開始研制D6AC，由AISI 4340 鋼改進而成，被廣泛用于制造戰(zhàn)術(shù)和戰(zhàn)略導彈發(fā)動機殼體及飛機結(jié)構(gòu)件。到了70 年代中期，D6AC 逐漸取代了其它合金結(jié)構(gòu)鋼，成為一種制造固體火箭發(fā)動機殼體的專用鋼種。美國新型地空導彈“愛國者”，小型導彈“紅眼睛”，大中型導彈“民兵”、“潘興”、“北極星”、“大力神”等，美國航天飛機的φ3.7m助推器殼體也采用D6AC 鋼制造。D6AC 還曾用于制造F-111飛機的起落架和機翼軸等。
標準：
ASTM A29/A29M-04
化學成分：
碳 C ：0.38～0.43
硅 Si：0.15～0.35
錳 Mn：0.60～0.90
硫 S ：允許殘余含量≤0.040
磷 P ：允許殘余含量≤0.035
鉻 Cr：0.60～0.90
鎳 Ni：1.65～2.00
銅 Cu：允許殘余含量≤0.025
鉬 Mo：0.20～0.30
力學性能：
抗拉強度 σb (MPa)≥1280(100),
伸長率 δ5 (%)≥12,
斷面收縮率 ψ (%)≥55,
沖擊功 Akv (J)≥78,
沖擊韌性值 αkv (J/cm2)≥98(10)
熱處理規(guī)范：
淬火850℃,油冷;回火600℃,水冷、油冷。
交貨狀態(tài)：以熱處理（正火、退火或高溫回火）或不熱處理狀態(tài)交貨，交貨狀態(tài)應在合同中注明。
